This project will study a peptide found in the sperm and semen of some species, that may enhance sperm fertility. Recently it was found that synthetic FertPlus' peptide, representing a 60 amino acid sequence within SGP-1 (highly conserved across species) detectable in human sperm and seminal plasma, improved fertility of roosters and turkeys in 6 robust experiments. It is hypothesized that: (1) some men (or roosters) are subfertile because their sperm have insufficient amounts of this SGP-1 fragment; (2) such deficient sperm are ineffective in achieving initial binding to the zona pellucida apparently necessary for subsequent strong binding, acrosome reaction and penetration; and (3) the percentage of sperm initially binding to the zona and pregnancy outcome achieved by certain subfertile men can be improved by in vitro exposure of their sperm to synthetic FertPlus'. Specific Aims for Phase I are: (1) screen populations of men to estimate the percentage for whom sperm-egg binding is improved by exposure of sperm to FertPlus and for whom fertility potentially might be improved; and (2) determine if sperm-egg binding of human sperm is reduced by conventional freeze-thaw procedures, and if binding of donor sperm can be improved by exposure to FertPlus' peptide. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE